|The Lo-Co Smart Valve instantly terminates hydraulic fluid flow in the event of a line break and does not require complicated microprocessors to distinguish between a line break and a normal flow surge. |
Having a hydraulic line become severed may result in dire consequences from the jet of hot oil that can spew from the end of an unrestrained hose. Even if serious injuries or equipment damage don’t result, cleanup costs — especially those occurring in sensitive environments — can be substantial. Velocity fuses pose one solution, but they still can allow relatively large quantities of hydraulic fluid to be lost before they terminate flow.
A better solution undergoing final development may be the Lo-Co Smart Valve, which is said to provide greater safety protection against the potential hazards, injuries, and expenses associated with catastrophic line breaks. “We designed the Lo-Co Smart Valve to offer full system safety protection in the event of a catastrophic line break,” states Donald M. Loper, president and founder of Lo-Co Safety Valve, LLC, Milwaukee. The Lo-Co Smart Valve can also be used to protect pumps from cavitation by shutting down systems if fluid level in a reservoir becomes dangerously low. In contrast to low-level reservoir switches, velocity fuses, and other safety devices, the Lo-Co Smart Valve can immediately stop pressurized fluid from escaping into the atmosphere the instant a line break occurs.
Limitations of velocity fuses In designing the Lo-Co Smart Valve, Loper says he took a close look at existing technology. “We determined that velocity fuses only offered limited protection to equipment subsystems, like cylinders. We wanted to create a valve that was smarter than a velocity fuse, more flexible than a hose break valve, and offered more protection than a load locking valve in the event of a catastrophic line break. In addition, our valve had to be designed to be more responsive than a low-level reservoir switch — it had to shut-off flow immediately, instead of shutting off flow when the tank is almost empty.”
Loper also took into account variables such as flow fluctuations and temperature and viscosity changes that are inherent to hydraulic systems. “Velocity fuses can’t distinguish between a flow surge and a line break, therefore, they offer only limited safety protection,” explains Loper. “Because most systems use opencenter directional valves, a velocity fuse placed in the pressure supply line would be subject to the constant flow surges that occur every time work is performed. These flow fluctuations would trip velocity fuses every time the operator shifted a valve out of neutral. This is the primary reason why velocity fuses are not a viable safety solution in the event of catastrophic line breaks.”
Hose-break valves can stop fluid from being released when a preset flow rate is reached, but they are not practical in systems where directional valves are constantly switched from a load to no-load condition. “To perform work, valves are continuously opened and closed; therefore, hosebreak valves will not work on many systems that are commonly used today,” continues Loper. “Additionally, if fluid viscosity changes, a hosebreak valve must be set to a different actuating flow rate to ensure troublefree operation.”
Lastly, Loper looked at load locking valves. “These valves are not designed to prevent high-pressure fluid from being released when a line breaks. A load locking valve only locks a load in place to keep it from free-falling,” explains Loper.
A smarter alternative
The Lo-Co Smart Valve, on the other hand, immediately shuts off the system’s pressure supply to prevent high-pressure fluid from escaping into the atmosphere. In the event of a catastrophic line break, pressurized fluid flows at relief-valve pressure back into the reservoir. If the system’s prime mover could not be immediately turned off, fluid would simply circulate through the relief valve and pump, thereby minimizing equipment damage, reducing fire hazards, preventing fluid injection injuries, and eliminating environmental contamination due to oil spills.
You might conclude that a computer chip or an electronic sensor allows the valve to distinguish the difference between a flow surge during normal equipment operation and a line break. However, Jean Kulig, vice president at Lo-Co Safety Valve explains that the Lo-Co Smart Valve is completely mechanical. “Our valve uses the physics of fluid power to safety shut-off flow.
“Ever since we showcased our Lo-Co Smart Valve design at the Milwaukee School of Engineering on July 13, 2007, we have enjoyed explaining repeatedly that our valve is placed in the pressure supply line and is not a velocity fuse. If a velocity fuse were placed in the pressure supply line it would trip every time the operator shifted a valve out of neutral. Our valve is smart; it knows the difference between the flow surges that occur when a valve is shifted and a line breaks.”
“The general consensus among the experts I have spoken to seems to be that the injuries and costs associated with line breaks are often under reported.Much of the information I have obtained deals specifically with the cost of oil replacement. Oil can range from $5 to $200 per gallon. Therefore, in the event of a catastrophic line break, a 20-gpm system could create a 10- to 40-gal spill,” states Kulig.